In recent years, as a method of synthesizing liquid fuels from a natural gas, a liquid-fuel synthesizing system using a bubble column reactor has been developed. In this liquid-fuel synthesizing system, a GTL (Gas To Liquids: liquid fuel synthesis) technique of reforming a natural gas to produce a synthesis gas containing a hydrogen gas (H2) and a carbon monoxide gas (CO) as the main components, synthesizing hydrocarbons using a catalyst with this synthesis gas as a source gas by the Fischer-Tropsch synthesis reaction (hereinafter referred to as “FT synthesis reaction”), and further hydrogenating and fractionating the hydrocarbons to produce liquid fuel products, such as naphtha (raw gasoline), kerosene, gas oil, and wax, has been used.
In the bubble column reactor, for example, as shown in Patent Document 1, a synthesis gas is blown into the reactor from the bottom of a slurry including a catalyst, and the synthesis gas rises through the slurry in the form of bubbles. Then, the synthesis gas is dissolved in a liquid of the slurry while rising through the slurry, and comes into contact with the catalyst particles to undergo the FT synthesis reaction, thereby producing gaseous or liquid hydrocarbons.